#include <stdio.h>
void to_binary(unsigned long n);

int main(void)
{
    unsigned long number;
    printf("Enter an integer (q to quit):\n");
    while (scanf("%ul", &number) == 1)
    {
        printf("Binary equivalent: ");
        to_binary(number);
        putchar('\n');
        printf("Enter an integer (q to quit):\n");
    }
    printf("Done.\n");
  
   return 0;
}

void to_binary(unsigned long n)   /* recursive function */
{
    int r;

    r = n % 2;
    if (n >= 2)
       to_binary(n / 2);
    putchar('0' + r);
  
    return;
}

今天的不懂之处：scanf(“%*s”);不知道怎么用